Four fire engines and 21 firefighters were called to a fire in a block of flats in Wyndham Road, Camberwell, in the early hours of Monday morning.
Forty families and residents were evacuated for the smoking 20-storey building, believed to have started inside a ground-floor storeroom.
Two men were seen fleeing the building before the fire brigade arrived. They both suffered burns and were taken to hospital by London Ambulance Service crews.
The Brigade was called at 1.22am and the fire was under control by 2.55am.
Fire crews from Peckham, Brixton and Old Kent Road fire stations attended the scene. The cause of the fire is under investigation by Brigade officers and the police